Computer networks may take a variety of forms. They may be located within a small, local geographic area, such as an office building, and consist of only a limited number of devices. This type of network is commonly referred to as a Local Area Network (LAN). On a broader scale, the networks may be larger and support more users over a wider geographic area, such as across a city or state. This type of network is commonly referred to as a Wide Area Network (WAN). On an even broader scale the LAN and WAN networks may be interconnected across a country or globally. An example of a globally connected public data communications network is the Internet. LANs and WANs are more likely to be private networks, that is, those which do not allow access by non-permitted computing devices.
Devices which may be associated with these networks may include personal computers, cellular phones, mobile data terminals, radio modems, portable computers, personal digital assistants, pagers, mainframes, departmental servers, mass storage devices, or any other similar device. A browser is a software program designed to help a user access information stored locally or on networks.
A proxy is a device or mechanism (usually an application program) on a network node which performs specialized functions and typically sits between the user's device and a network. One such function is to provide network security. Security is provided between a private and public network by requiring communications (e.g., information exchanges) to pass through the proxy. Another function of a proxy is to store or cache recently accessed information (e.g., copies of documents and images). If a browser desires information which is located outside the local network, that is to say on an information source attached to an external network, communications pass from the browser through the proxy before going on to the external network.